Dengue fever is a viral infection that is spread through the bite of particular breeds of mosquito. It is widespread across the Pacific Island countries, Asia, central and southern America and Africa.
|See your doctor if you are unwell after travel to a dengue-affected area, or call Healthline (free in New Zealand) on 0800 611 116 for advice.|
- The common symptoms of dengue fever are fever, severe headache, pain behind your eyes, pain in your joints and muscles, and a rash (usually 2–5 days after the fever starts).
- Seek immediate medical attention if you have the above symptoms or are unwell after travel to dengue-affected areas such as the Pacific Islands, Asia, central and southern America and Africa.
- In rare cases, dengue fever can worsen to a severe form called dengue haemorrhagic fever or dengue shock, which can cause death. You are at greater risk of this if you have had dengue before and are infected with a different strain of the virus.
- If you make a number of visits back to a dengue-affected country over the years, you are at risk of picking up dengue fever repeatedly.
- There is no vaccination to protect against the disease, so preventing mosquito bites is the best form of protection.
- If you are travelling to dengue-affected countries use insect repellent, wear protective clothing and stay in places where there are mosquito screens on windows and doors.
What causes dengue fever?
Dengue fever is caused by the dengue virus which is spread through the bite of particular breeds of mosquito (Aedes mosquito). These mosquitoes are prevalent in Pacific Island countries, Asia, central and southern America and Africa. It is not present in New Zealand. Although the most common time for mosquito bites is early morning and late afternoon, dengue-carrying mosquitoes bite all through the day.
Mosquitoes become infected with dengue after biting sick humans who have dengue virus in their blood. If an infected mosquito bites someone else between 8 and 12 days later, it can pass on the dengue virus. There are 4 types of dengue viruses known to cause disease in humans. A person infected with one type of dengue will only become immune to that type. They will not be immune to other types of dengue and could be at higher risk of severe disease if they contract another type.
Dengue fever cannot be spread directly from person to person.
What are the symptoms of dengue fever?
Symptoms of dengue fever tend to develop within 4 to 7 days of being bitten by the infective mosquito. The common symptoms of dengue are:
- sudden fever
- severe headache
- pain behind your eyes
- feeling very tired
- muscle and joint pain (ankles, knees, elbows)
- rash on your arms and legs, severe itching, peeling of skin
- nausea (being sick) or vomiting (being sick).
Generally, younger children and those with their first dengue infection have a milder illness than older children and adults.
|Get checked if you are unwell after travel to dengue-affected areas such as the Pacific Islands, Asia, central and southern America and Africa, or call Healthline (free in New Zealand) on 0800 611 116 for advice.|
Severe dengue or dengue haemorrhagic fever
In rare cases, dengue fever can worsen to a severe form called dengue haemorrhagic fever or dengue shock. This can cause severe bleeding, shock, multiple organ failure, brain or heart damage and death. This can occur in both adults and children. You are at greater risk of this if you have had dengue fever before, and are infected with a different strain of the virus. This is important if you make a number of visits back to a dengue-affected country over the years, as you are at risk of picking up dengue fever repeatedly.
Initially, severe dengue has the same symptoms as above, but after a few days, your condition worsens rapidly.
|Seek immediate medical attention if any of the following warning signs appear:|
Dengue haemorrhagic fever can cause death in about 5% of cases (5 in every 100 people affected with the disease), mostly children and young adults.
How is dengue fever diagnosed?
See a doctor immediately if you think you may have dengue virus. Early diagnosis is important to reduce the risk of complications.
Your doctor will ask about your symptoms, including any recent travel, and will do a physical examination. Blood tests are required to diagnose dengue fever.
How is dengue fever treated?
Many people infected with dengue have only a mild illness and often are not even aware they have been infected. There's no specific medical treatment for dengue. Your doctor may advise you to:
- have bed rest
- drink plenty of fluids
- take medicines such as paracetamol to reduce fever and ease pain. Do not take aspirin or non-steroidal anti-inflammatory agents such as ibuprofen, naproxen or diclofenac because they can increase the risk of bleeding.
The illness usually lasts up to 10 days but recovery may take some time; you may feel tired and depressed for weeks.
For people who show warning signs of severe dengue (dengue haemorrhagic fever or dengue shock), hospital admission is required. Treatment may include drips (intravenous fluids and replacement of lost electrolytes).
How is dengue fever prevented?
There is no vaccine to prevent dengue. The best way to avoid infection in areas where there are dengue-carrying mosquito populations is to protect yourself against being bitten and to reduce potential mosquito breeding sites. All people in dengue-affected areas, whether you have been previously infected or not, should take precautions to prevent being bitten.
Protecting against mosquito bites
- Use screens on doors and windows.
- Use insect sprays.
- Use mosquito coils.
- Use a mosquito net over your bed at night. New bed nets often have insecticide already on the net but, if not, you can spray the net with insecticide.
- Turn on air conditioning if you have it and close all windows and doors – this is very effective at keeping mosquitoes out of the room.
The dengue-carrying mosquito can be around during the day so keep covered, day and night.
- Wear an insect repellent cream or spray containing no more than 35% diethyltoluamide (DEET). Higher concentrations are no more effective and can be harmful. Products containing 20–25% picaridin or 30% lemon eucalyptus oil can also be used.
- When using sunscreen, apply repellent over the sunscreen.
- Wear light-coloured protective clothing such as long-sleeved shirts, long pants and hats.
- Apply repellent to clothes.
- Wear shoes rather than sandals.
- Use zip-up screens on tents.
- Avoid areas where mosquitoes are most active.
The mosquito that transmits dengue is commonly found in urban areas, so avoiding rural travel will not protect you against dengue fever.
Reduce mosquito breeding sites
Dengue-carrying mosquitoes generally breed in stagnant water found in containers (eg, discarded tyres, uncovered barrels, buckets) rather than in rivers, swamps, open drains, creeks or mangroves. The disease is particularly common in urban areas where standing water is near to homes and provides an ideal breeding ground for the carrier mosquitoes. To eliminate breeding sites:
- empty any containers that hold water in and around the place you are staying
- cover all water tanks, cisterns, barrels, rubbish containers
- remove or empty water in old tyres, tin cans, bottles, trays
- check and clean out clogged gutters and flat roofs where water may have settled
- change water regularly in pet water dishes, birdbaths and plant trays
- trim weeds and tall grasses, as adult mosquitoes seek these for shade.
Countries often affected with dengue fever include:
- North Queensland, Australia
- Pacific Islands, eg, Fiji, Cook Islands, Marshall Islands, Kiribati, New Caledonia
- Samoa, Tonga and Vanuatu
- Asia (including Cambodia, India)
- Latin and South America.
Dengue outbreaks can occur anywhere in tropical countries as shown in the map below, so if you are planning on travelling, check the risk level before you go.
Dengue Ministry of Health, NZ (Fijian, Samoan, Tongan)
Dengue fever (Samoan, Fijian, Tongan, Cook Island Maori) Auckland Regional Public Health Service, NZ
Avoiding bug bites while travelling Ministry of Health, NZ
Travel advice Safe Travel, NZ
Insect repellent DermNet, NZ
Insecticides and the skin DermNet, NZ